This invention relates to air separator apparatus comprising a rotor adapted to be charged centrally with material to be separated and having feed passages extending radially outward for the material to be separated and extraction openings arranged between such feed passages. The apparatus comprises at least one extraction housing fixedly arranged in axial extension of the rotor and adjoining the extraction openings of the rotor, thereby enabling separation air to flow substantially inward through the space situated between adjacent feed passages and enter the extraction housing together with the fine material through the extraction openings of the rotor, while the coarse material is thrown outward.
One air separator of the general type to which the invention relates is described for example in German Pat. No. 2,225,258. It is distinguished from other known types by a considerably higher throughput of material to be separated for the same diameter and by a relatively simple construction.
In the air separator described in German Pat. No. 2,225,258, the rotor consists essentially of two cover discs between which several ribs are radially arranged to form feed passages for the material to be separated. One of the two cover discs is provided between adjacent feed passages with openings forming the extraction openings of the rotor through which the separation air enters the stationary extraction housing arranged below the rotor together with the fine material. In this known separator, therefore, the space situated between the outer end of the feed passages and the extraction openings is axially delimited by one of the cover discs of the rotor.
The above-mentioned outer annular region of the lower cover disc of the rotor according to German Pat. No. 2,225,258 inevitably undergoes a certain amount of wear in operation, both on its upper surface delimiting the flow space for the material to be separated and also on its lower surface which, together with the opposite stationary wall of the extraction housing, forms a sealing gap. In addition, it becomes increasingly more difficult from the constructional point of view to maintain the required sealing gap with increasing rotor diameter.